The information on the inhibitory effect of propafenone in vascular
smooth muscle is sparse. Propafenone acts through blockage of
voltage-dependent cardiac Na+ channels, L-type Ca2+ channels,
voltage-sensitive K+ (Kv) channels, as well as -adrenergic receptors in
the heart. The introduction of different chemical groups in the benzyl
moiety of propafenone influences pharmacological properties of newly
developed derivate of propafenone. Here we investigated the effect of
new ortho-chloro derivate of propafenone (5OCl) on the vascular tone
of precontracted rat aorta. 5OCl produced endothelium-independent
relaxation of rat aorta. In order to test the involvement of different ion
channels in 5OCl mechanism of action, antagonist of Na+, lidocaine, KV
channels, 4-aminopyiridine (4-AP) and L-type Ca2+ channels,
nifedipine were used. All tested antagonists of ion channels did not
influence the relaxation of rat aorta induced by high a concentration of
5OCl (10 M), but antagonized the relaxation induced by low
concentrations of this propafenone derivate. Thus, 5OCl derivate has
comparable potency and efficacy as propafenone. According to its
interaction with lidocaine, 4-AP and nifedipine it seems that 5OCl partly
shares the mechanism of action with propafenone. The mechanism of
vasodilatation induced by high micromolar concentration of 5OCl is not
defined and further investigations are necessary.